First of all let me say i am no expert ,but i have built and bought my fair share of minnow traps in my day. Gee makes a great trap you can find them at most fishing stores, you now the wire mesh cylinders. usually sold between 8-12 bucks.
I've also gone to the hardware store and bought "hardware cloth" same stuff that most minnow traps are made of comes in 1/8th inch mesh, 1/4 and 1/2 inch mesh sizes (use the 1/4 its pretty good not to small and not to big.) It also comes in varing widths from 1' to 4' and is usually sold by the foot. Last time I bought some here in Maine it was around $3 something a foot for 2' wide 1/4 mesh. I've gone and rolled the mesh and cut off one side of the mesh so that the wire strands stuck out and proceeded to fold/bend/weave it into a cylinder shape, then I used a bucket to cut out a circle and cut it to the center and then same thing cut/fold/weave into a cone shape. then cut my opening for the "funnel" and then attach using same method to cylinder. for a door I just cut out a section, and then cut a bigger piece so it overlaps on edges and used hog rings on hindge side and a rubber band w/ two wire hoods to strecth and catch the mesh, basically holding door closed(we use the same set up on our lobster traps, door wise anyways)
Ive also used 3/4 square stock pieces of wood, made 4 square frames attached the mesh using staples, hindged the two haves so I could open it, made my "funnels" and attached them to the ends. I used a hoo and eye for the latch, and a screw eye to attach the line to so I could pull it up.
Just remember to check your local regs on it though, as you may have to have your traps marked with your name, address, and also if your gonna cut a hole in the ice and lower it down tie your line to a stick and lay it accross your hole(allows your line to stay in the middle, so when you come back and have to chip it out you wont cut your line.
hope this helps
